My team has used polycord many times over the years with plenty of success. We first used it in ZoneZeal, but we used 1" wide flat belting material that was melted together. In Aim High, we used 1/4" round solid core, also melted together. It was a bear to melt together all the pieces but it worked wonderfully. After that year we discovered hollow core belting, which is much easier to work with and yields the same result, never had a belt snap.
aaaaaaaaaand this is where I'm probably going to get either a slap or a hand shake from everyone reading, this is a very polarizing design...
In Lunacy, my senior year, we had the brilliant idea to combine the flat belting and the solid core tubing... by melting them together. This design was then fed through the gap in 80-20, and we got a... brush. Behold,
our robot from 2009.
...yeah, we did that. And it was awesome.